The present invention relates generally to electrodes for electrochemical batteries, and more particularly to a method for creating a desirable battery electrode porosity for a given set of battery characteristics and application parameters.
Electrochemical batteries are used in a variety of applications. Electrochemical batteries convert chemically stored energy into electrical energy. Electrochemical batteries contain an anode, a cathode, and an electrolyte. The anode and the cathode may be produced from the following materials: lead, copper, steel, titanium, nickel, ceramic, polymers, or other various materials known in the art. The electrolyte may be composed of water, an organic compound, a gel or a conductive solid. The electrolyte may also contain a salt or an acid. An electrical potential exists between the anode and the cathode that creates an electrical current through the electrolyte from the cathode to the anode.
Electrochemical batteries have become the main power sources in many applications such as electric vehicles. Many electric vehicles use valve-regulated lead-acid (VRLA) batteries. Limitations in the use of VRLA batteries relate to issues of imposed electrolyte concentration gradients. Imposed electrolyte concentration gradients cause lower electrochemical battery discharge performance. The chemistry of VRLA batteries is particularly susceptible to a deficit of electrolyte at low states of charge, which can cause the battery voltage and energy output to drop precipitously.
The concentration of electrolyte at an electrode active site is a major contributor in a battery polarization function, particularly at low states of charge. As the electrolyte is consumed, the progressively lower concentration leads to more pronounced concentration polarizations. It has been further discovered that diffusion of the electrolyte through the electrode itself may become a limiting process if current densities of the electrolyte are sufficiently high.
Various solutions have provided methods for monitoring certain operating characteristics such as state-of-charge, temperature, and terminal voltage of an electrochemical battery. In so monitoring various characteristics, rating values of a particular electrochemical battery have been quantified such as discharge rate, capacity, and cycle life. In evaluation of the various operating characteristics in correlation to the resulting rating values, improvements to electrochemical batteries have been proposed. The proposed improvements include adjusting or changing the type, size, and quantity of the materials used, but these proposed improvements have not been sufficient in optimizing electrolyte diffusion.
Therefore, a need exists to optimize diffusion of the electrolyte thereby increasing the capacity, the discharge performance, and the cycle life of electrochemical batteries.
Moreover, it is desirable to optimize the diffusion of the electrolyte for various applications having different requirement needs.
Accordingly, the present invention provides an improved manufacturing method for increasing the performance of a battery. An advantage of the present invention is that it provides a method of optimizing the diffusion of an electrolyte within a battery for various applications.
The foregoing and other advantages are provided by a method of determining the optimum porosity for a set of battery electrodes for a given application and a method of manufacturing the battery electrodes having the determined optimum porosity.
A method is provided for calculating desired porosity of battery electrodes of a battery during the manufacturing of the battery electrodes using an electrochemical model and a thermal model of the battery including determining energy and current requirements for a particular application. Characteristics of the battery in response to said energy and current requirements are determined. The battery characteristics and energy and current requirements are prepared for use in the electrochemical model and the thermal model. Porosity of the battery electrodes is determined by solving equations within the electrochemical model and the thermal model. Porosity of the battery electrodes are varied until voltage potential across the battery varies by less then a predetermined tolerance factor for an operating range state of charge.
A method of manufacturing battery electrodes for a battery is also provided, which includes determining desired battery electrode porosity for a particular application. A paste mixture is created in response to the desired battery electrode porosity. The paste mixture is applied to a grid followed by curing of the grid and paste.
One of several advantages of the present invention is that it determines the optimum porosity for a given set of battery electrodes of a particular electrochemical battery at which diffusion no longer substantially limits battery performance.
Another advantage of the invention is that it provides a technique for fabricating battery electrodes having optimum porosity.
Another advantage of the present invention is that it provides a method of determining the optimum battery electrode porosity without physically building the battery electrodes. This reduces time and costs in building and testing of the battery.
Therefore, the present invention by providing a manufacturing method for a battery having battery electrodes with optimum porosity, also provides a technique for constructing a battery for a particular application that has increased capacity, performance, and cycle life.
The present invention itself, together with further objects and attendant advantages, will be best understood by reference to the following detailed description, taken in conjunction with the accompanying drawing.